After providing all the funding for The Brain from Top to Bottom for over 10 years, the CIHR Institute of Neurosciences, Mental Health and Addiction informed us that because of budget cuts, they were going to be forced to stop sponsoring us as of March 31st, 2013.

We have approached a number of organizations, all of which have recognized the value of our work. But we have not managed to find the funding we need. We must therefore ask our readers for donations so that we can continue updating and adding new content to The Brain from Top to Bottom web site and blog.

Please, rest assured that we are doing our utmost to continue our mission of providing the general public with the best possible information about the brain and neuroscience in the original spirit of the Internet: the desire to share information free of charge and with no adverstising.

Whether your support is moral, financial, or both, thank you from the bottom of our hearts!

Bruno Dubuc, Patrick Robert, Denis Paquet, and Al Daigen




Tuesday, 13 October 2020
Our perceptions are shaped by the possibility of imminent actions

Affordances are a key concept in cognitive science, first advanced by J.J. Gibson in 1966. As I explained in an earlier post in this blog, an affordance is an opportunity that an object offers to take action. A hammer, for example, offers the opportunity to be grasped by its handle, and a chair offers the opportunity to sit down. What is interesting about this concept of affordances is that the opportunity for action does not depend on an object’s characteristics in any absolute sense, but instead is relative: it depends on the possible relationships that a particular organism may establish with that object. A tree, for example, offers different affordances to humans, who may use it as shelter from the rain, or crows, which may use it as a perch, or to woodpeckers, which may use it as a place to hunt for food. Moreover, as the above illustration suggests, any given object (again, such as a tree), may inspire different affordances for a given organism (such as a human) depending on that organism’s motivations and/or the broader general situation,

There is a large body of neuroscientific research, notably including the studies by Paul Cisek and his colleagues, showing that the brain is constantly simulating the actions suggested to it by the affordances that it perceives in its environment. In physical terms, this means that certain populations of neurons begin to increase their activity with a view toward possibly increasing it even further to actually carry out the actions suggested to them by the affordances that their environment suggests to them. These studies showed that certain “pre-motor” areas of the brain were thus activated in our day-to-day perceptions, which therefore operate to identify objects’ affordances much more than their physical characteristics such as size, colour, and shape.

But what about the brain’s sensory regions themselves, such as the primary visual cortex? Surely they can’t be “contaminated” by signals from affordances in the outside world, because that might prevent them from doing their jobs as “objective” sensors of the properties of objects. And yet the brain’s sensory areas, just like its motor areas, are in fact affected by affordances, as was shown by Zakaria Djebbara and his colleagues in a study published in the journal PNAS in July 2019.

In this study, subjects wore virtual-reality headsets, along with electroencephalogram sensors that recorded their brain activity as they performed a task in the virtual reality environment. The task began in a virtual-reality room with a door in one wall, leading to another room. In each trial of the task, the door could be any one of three widths: too narrow to pass through, just wide enough to pass through, and wide enough to pass through easily. When the wall turned red, the subjects didn’t have to do anything. But when the wall turned green, the subjects had to try to walk through the door. The researchers made two very interesting observations. First, the type of neural activity in the subjects’ primary visual cortexes depended on the affordance offered by the door, that is, whether or not the subjects perceived it as passable. But second, and even more interesting, this dependency was observed only when the wall was green—in other words, when the subjects knew that they were going to have to try to pass through the door.

These findings suggest that the subjects actually saw the door differently both according to the affordances (degrees of passability) that it offered and to the situation at hand (whether or not the subjects had to try to pass through the door). In other words, as Gepshtein and Snider might put it, these findings support the ideas that our perceptions are shaped by the possibility of imminent actions.

Uncategorized | Comments Closed


Wednesday, 30 September 2020
The expertise account, or, why the brain’s face-recognition area can be activated by the sight of a chessboard

In a 2017 article on the chess website chessable, entitledBeating Magnus after a month of training: the neuroscience of why learning chess is so much harder than learning a language”, author David Karmaley writes: “A fascinating finding from neuroscience is that your brain starts using the fusiform face area to store chess positions! This is the part of the brain usually responsible for human face recognition.”

Karmaley seems surprised that a part of the brain associated with face recognition is also used to recognize the positions of pieces on a chessboard, and at first glance, the connection may seem puzzling. But a theory known as the expertise account offers a highly plausible explanation. (more…)

From the Simple to the Complex, From Thought to Language | Comments Closed


Wednesday, 9 September 2020
The combined effects of meditation and magic mushrooms

Today I want to tell you about a study entitled “Psilocybin-assisted mindfulness training modulates self-consciousness and brain default mode network connectivity with lasting effects,” which a research team from the University of Zurich published in the journal NeuroImage in August 2019. As the title suggests, this study combined two methods of modulating the brain: engaging inmindfulness meditation and taking the hallucinogen psilocybin, a psychoactive molecule found in “magic mushrooms”. Previous studies had shown that both of these methods produced a similar effect: they gave subjects the impression that the boundaries between their bodies and their environments were dissolving (a state of consciousness often referred to as ego dissolution). But in this study, the research team wanted to find out whether combining these two methods might make this effect stronger and longer-lasting. (more…)

The Emergence of Consciousness | Comments Closed


Tuesday, 18 August 2020
How labelling brain parts functionally can be overly simplistic: the cerebellum as a case in point

Today I’d like to talk about the cerebellum. To introduce this topic, I’ll remind you that as animals’ bodies evolved and became more complex, they were subjected to greater adaptive pressures to move more and more efficiently, and the cerebellum is a brain structure that was closely involved in this process.

Here’s the most surprising fact about the cerebellum. The human brain as a whole contains about 86 billion neurons. The cerebral cortex accounts contains about 16 billion of these neurons and accounts for about 80% of the brain’s weight. In contrast, the cerebellum accounts for only about 10% of the brain’s weight, but contains nearly 69 billion neurons! Thus more than three-quarters of the neurons in the human brain are located in the cerebellum, even though it is a small structure compared with the brain as a whole. (more…)

Body Movement and the Brain | Comments Closed


Tuesday, 21 July 2020
How neuronal communication began, and how brains differ from computers

When you move through space, your sensory perceptions change constantly, in real time. What we call cognition can be equated with this uninterrupted flow of perception and action through by a body and a brain located in an environment. But as scientists have now told us, the modern human brain contains many neurons that are neither sensory nor motor—so many that it can sometimes be hard to realize that this perception/action loop is still the foundation of the nervous systems of primates and other animals. These interneurons, as they are called, receive nerve impulses from sensory neurons and transmit signals to other neurons, and so on. And at some point in time, after all sorts of indescribably complex detours, a motor neuron will receive signals from some of these interneurons and then be able to command a muscle to contract to make a body part move.

What distinguishes the nervous system from other communication systems in the human body, such as the endocrine and immune systems, is its speed. The time that elapses between a perception and a suitable bodily action in response can be a second or less. How do the myriad neurons in the nervous system manage to communicate with one another so rapidly? (more…)

From the Simple to the Complex | Comments Closed